The present invention relates to a power amplifying unit implemented with a power amplifying module and, more particularly, to a power amplifying unit connectable to a transmitter/receiver of a mobile radio telephone apparatus.
Today, a mobile radio telephone apparatus is available in a variety of configurations and has a transmitter/receiver therein. A power amplifying unit, or booster, is connected to the transmitter/receiver in order to amplify a transmission output to a desired power before radiating it via an antenna or to amplify a signal coming in through the antenna before feeding it to the receiver. In many boosters for such an application, an amplifier for amplifying a transmission output is implemented with a power amplifying module (sometimes referred to as a PA module hereinafter). A PA module contributes a great deal to the miniaturization and mass production of boosters as well as to the simplification of a heat radiation structure. Various types of PA modules are commercially available, and each has at least a control voltage terminal for receiving a control voltage from a DC current amplifier which is a control element included in the booster. Generally, the maximum control voltage that may be applied to the control voltage terminal differs from one PA module to another, depending on the circuit design and the kind of transistors and other elements used. On the other hand, a power source voltage applied to the DC current amplifier is usually a fixed voltage. Hence, the PA module usable with the power amplifying unit or booster is limited to a particular type which allows the fixed voltage to coincide with the maximum control voltage.